Building source heat pump

ABSTRACT

An energy efficient heating and cooling system is defined by a closed loop coil system of conduit in which the tubing through which fluid flows is located to the interior of the structure, preferably above the winter-heated space and below an insulated roof or in a multi-level building floor, so that heat rising to the ceiling may be recovered in a geothermal heat pump. The structure source loop may be combined with an optional ground source loop. A furnace controls the flow of heated air into the structure and supplies supplemental heat and the system is under the control of a microprocessor.

TECHNICAL FIELD

This invention relates generally to heating and cooling systems for structures such as homes and buildings, etc. and more specifically to such structures utilizing a heating and cooling system that utilize a heat pump in which heat within the structures is used to support the heat pump, thus recycling energy that otherwise would escape from the structure.

BACKGROUND OF THE INVENTION

Heating and cooling systems that utilize a buried ground coil through which a medium passes for heating by earthen material are typically called “geothermal systems.” Briefly described, geothermal heating and cooling systems circulate a fluid heating medium through coils of tubing that are buried in the ground or immersed in a pond. The earth acts as a source of heat; the fluid is heated as it is circulated through the coils in the ground and is then pressurized prior to flowing through a heat exchanger such as a heat pump, which may be of the liquid-to-air type or liquid-to-liquid type. The heat derived in the heat pump from the relatively warmed fluid is used to heat a structure. The fluid, cooled by passage through the heat exchanger, is directed back to the buried ground coil where it is again warmed by the heat retained in the earth.

There are of course many variations on this basic theme. Some geothermal systems are of the “closed” type, where the loops that circulate the heating medium are in a fully close loop that is buried in the ground. Other systems are “open.” In an open loop system, ground water is pumped through a geothermal heat pump where heat is drawn off the liquid. The relatively cooled water is then discharged into a pond. As noted above, a “geothermal” system may also contemplate immersion of the coils in a pond. In this sense, a body of water also acts as a heat source that may be utilized to warm the medium that flows through the coils.

In addition to geothermal heating and cooling systems, conventional electric heat pumps are used ubiquitously because all of these kinds of units help make usage of energy more efficient. Nonetheless, as energy resources become more scarce, and as demand for energy increases, there is a substantial need for heating and cooling systems that use energy more efficiently. As a corollary, as energy becomes more expensive the demand for energy-efficient heating and cooling systems increases as a matter of economics: the less energy that is used, the less the cost of purchasing the energy.

There is a significant need therefore for efficient heating and cooling systems for homes and buildings.

SUMMARY

The present invention is an improved method and apparatus for efficiently heating and cooling a structure such as a residence, commercial building, etc. The system utilizes a closed loop system similar to a closed loop geothermal heating system but locates the coils in the system to the interior of the structure in a location where the coils are able to be heated by relatively warm air that is used to heat the building. The structure may utilize an optional heating system such as a geothermal heating system, furnace or a conventional electric heat pump. The closed loop system that is located in the interior of the structure is configured to capture heat from the interior of the structure and use that heat to warm the heating medium in the coils.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a structure having a heating and cooling system according to the present invention.

FIG. 2 is a schematic view showing the components of the heating and cooling system according to the present invention in isolation.

FIG. 3 is a plan view of an alternative arrangement of the interior coils used in accordance with the present invention.

FIG. 4 is an isolated schematic view of the control system according to the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

With reference to FIG. 1, the heating and cooling system 10 according to the present invention is illustrated in a first embodiment in a structure 12 such as a typical residential building. It will be understood that structure 12 is shown as a residential type of building only to illustrate the invention, which could be used with any kind of structure, including multiple story structures. Heating and cooling system 10 comprises several different components, each of which is described in detail below, including a furnace 14, a geothermal heat pump 16, an optional ground source loop 18, a structure source loop 20 and a controller 22 that is under the control of a microprocessor and which is functional to control operation of the entire system. The structure 12 illustrated in FIG. 1 is typical of a residence that includes a below-ground-level basement 24—the furnace 14, geothermal heat pump 16 and controller 22 are all located in the basement. It will be appreciated that the heating and cooling system 10 may be incorporated into any kind of structure, including commercial buildings and the like, and of course it is not necessary that the building include a basement.

Individual components of heating and cooling system 10 will be described beginning with furnace 14. The furnace used with the present invention may be any kind, including conventional forced air gas-fired or electric furnaces, and other “furnace” types including radiant floor heating. The purpose of furnace 14 is to provide heat and cooling to structure 12. Accordingly, it will be appreciated that the term “furnace” is used generically herein to describe any heat source for heating and cooling structure 12. Nonetheless, the furnace 14 illustrated herein is conventional and is under the control of a thermostat 26 that regulates operation of the furnace, and which typically is located in a convenient place in structure 12. Different thermostat configurations may be used, for example, thermostats that rely upon various zones. The furnace illustrated herein includes conventional ducting 28 and a fan shown schematically at 29 that delivers heated (and cooled) air to the interior of the structure, and as shown in FIG. 2, conventional return air ducting. It will be appreciated based on the description below that the fan 28 operates not only to deliver air heated by the furnace 14 to structure 12, but also to deliver air heated and/or cooled by operation of geothermal heat pump 16 to the structure. Therefore, if the “furnace” used in structure 12 is of the type that normally would not include a fan, such as a radiant floor heating system, then fan 29 and ducting 28 will be connected to the heat pump 16.

Geothermal heat pump 16 also is a conventional unit that essentially functions as a medium-to-air heat exchanger where heat carried into the heat pump from one of the source loops (i.e., either the structure source loop 20 or the ground source loop 18) is drawn off in the heat pump and transferred into the forced air conduit system of furnace 14 so that the heat may be used to warm structure 12. The geothermal heat pump 16 may be of any known type, such as an air-to-water heat pump, or a water-to-water type. With reference to FIG. 2, the geothermal heat pump 16 comprises a conventional heat pump unit 30 (which as noted may be of any type) that is connected through controller 22 to both source loops—that is, structure source loop 20 and ground source loop 18.

As noted, ground source loop 18 should be considered optional in the present invention. Generally described, a ground source loop system relies upon the relative temperature of the ground to heat or cool a heat exchange fluid flowing through coils that are buried in the ground. As relatively cool fluid flows from the cool side of the system and is circulated through the coils, the fluid is either warmed or cooled by the ground. The relatively warmed or cooled fluid is drawn off or extracted in a heat pump, which functions as a heat exchanger, to supply warm air or cool air, as the case may be, to structure.

The ground source loop 18 shown in the figures comprises a length of conduit or tubing defined as ground loop coils 32 which are buried in the ground at an appropriate depth. The ground loop coils 32 could just as well be submersed in a pond. A horizontal ground loop system is illustrated in FIG. 1, but it will be appreciated that the ground source loop 18 may utilize many other different configurations such as pond loops, vertical ground loops, open loops, etc. The ground loop coils 32 illustrated in FIG. 2 show a typical winter configuration having a cool side 34 and a warm side 36. Relatively cool exchange fluid exiting heat pump unit 30 enters the ground loop coils 32 in cool side 34. As the fluid flows through tubing 38, the exchange fluid is warmed by the heat of the earth, resulting in the “warm side” 36 being at the “downstream” end of the tubing. Heat exchange fluid flowing from the warm side 36 enters the heat pump unit 30 where the heat is drawn off for heating structure 12. The tubing 38 used to define ground loop coils 32 is preferably conventional, and the length of tubing used in the ground loop is variable depending upon the particular installation. Various heat exchange fluids may be circulated through the loops. Briefly and generally described, geothermal heating systems such as ground source loop 18 utilize the heat storage capacity of the earth or ground water to heat fluid flowing through the ground loop coils.

The structure source loop 20 according to the present invention is similar to the ground source loop 18 but is located in a different location and derives heat from different sources. Structure source loop 20 is connected to geothermal heat pump 16 through controller 22 and, assuming that structure 12 includes a ground source loop 18, defines a second heat exchange system used in structure 12. The structure source loop 20 illustrated in FIG. 2 shows a typical winter configuration in which the loops define a cool side 42 and a warm side 44. As described above, relatively cool exchange fluid enters the tubing of structure source loop 20 from heat pump unit 30 in the cool side 42. The heat pump unit 30 is thus in discharge and receiving communication with the conduits of the structure source loop. The fluid medium is warmed as it circulates so that when the fluid returns to the heat pump unit it is returning at warm side 44. Structure source loop 20 is necessarily a closed loop system, whereas when a ground loop source 18 is used, it may be an open loop system. As with ground source loop 18, the tubing 46 used in structure source loop 20 is conventional and the fluid that circulates through the tubing may be of various types of refrigerant fluids.

Returning to FIG. 1, it may be seen that the tubing 46 of structure source loop 20 is connected through controller 22 to heat pump 16 and is preferably plumbed through the walls of structure 12 or through a chase. The conduit or tubing runs upwardly through the walls and is installed in a series of loops above the heated space 48 (sometimes referred to herein as “winter-heated space”) in the interior of structure 12. As air in the interior of structure 12 is heated, whether by furnace 14 or otherwise, the warm air rises toward the ceiling 50. By positioning the tubing of structure source loop 20 above the winter-heated space 48, the fluid circulating through the tubing 46 is heated by the warm air. This heat is then recovered from the fluid in geothermal heat pump 16 in the same manner that heat from ground source loop 18 is recovered in the heat pump.

It will be appreciated that there are numerous equivalent manners in which the tubing 46 of structure source loop 20 may be installed above the winter-heated space 48, and further that the length of tubing used in any particular installation, including the length of tubing installed above the heated space, will vary. Preferably, the length of tubing installed above the heated space provides substantial surface area for exchange of heat from the warm air in the structure to the heat exchange fluid flowing through the conduit. With reference to FIGS. 1 and 3, the tubing 46 is shown in a first illustrated embodiment installed between roof structures such as trusses 52 and above the finished ceiling layer 54. A layer of insulation 56 is installed above the tubing 46 in order to minimize exposure of the tubing to any temperature fluctuations from the exterior of the structure. Alternately, tubing 46 may be installed so that the loops run in a direction that is generally transverse to the trusses. The finished ceiling layer 54 may include vents and other architectural features that allow free circulation of heated air from the structure to the tubing 46. Moreover, the entire structure source loop 20 may be installed so that the tubing itself is in the interior of the structure in the winter-heated space 48. In this respect, it will be understood that the structure source loop 20 is installed above the winter-heated space, but below the roof 51, and with a layer of insulation 56 interposed between the tubing and the roof.

Regardless of the particular manner in which the coils of structure source loop 20 are installed, insulation is used between the tubing and the roof to ensure that the loop 20 is exposed to the interior of the structure but is insulated from cold air above the insulation and the exterior of the structure.

With reference now to FIGS. 2 and 4, controller 22 is shown schematically to comprise a flow control system with valves 58 and 60 that are multiport valves connected to both the ground source loop 18 and structure source loop 20. Valves 58 and 60 are configured for selecting either ground source loop 18 or structure source loop 20 and directing the fluid flow from the selected loop to geothermal heat pump 16. As shown in FIG. 4, controller 22 includes two automated multiport valves 58 and 60, each of which are preferably electrically actuated under the control of a microprocessor 62. Microprocessor 62 communicates with thermostat 26 through data line 64 and to the valves 58 and 60. As noted, controller 22 is configured for selecting either ground source loop 18 or structure source loop 20. When structure source loop 18 is selected, valves 58 and 60 are operated under the control of microprocessor 62 to define a flow path from warm side 44 through valve 58 and through warm side tubing 66 to geothermal heat pump 16. Heat is exchanged in heat pump 16 and the cooled fluid is routed through cool side tubing 68 through valve 60 into cool side 42 of the structure source loop.

On the other hand, when ground source loop 18 is selected, microprocessor 62 operates valves 58 and 60 to define a flow path from warm side 36 through valve 58 and through warm side tubing 66 to heat pump 16. The cooled fluid is routed through cool side tubing 68 through valve 60 into cool side 34 of the ground source loop. It will be appreciated by those of ordinary skill in the art that one or more pumps are required as means to control flow of fluid through the structure source loop and ground source loop, and that the pumps are also under the control of microprocessor 62. Pumps 59 and 61 are shown schematically in FIG. 2 for structure source loop 20 and ground source loop 18, respectively. For example, the pump 61 that controls fluid flow through ground source loop 18 is inactivated when structure source loop 20 is activated, and so on. Further, multiport valves 58 and 68 may include additional ports that allow for recirculation of coolant through the loops bypassing the geothermal heat pump 16.

Operation of the heating and cooling system 10 will now be detailed in a first preferred embodiment in which a structure source loop 20 is used in structure 12, but a ground source loop 18 is not used. It should be understood that the invention described herein relates primarily to the structure source loop 20. The structure source loop 20 may be combined with a ground source loop 18 as described, but the ground source loop is optional. Thermostat 26 serves as the primary user interface for control of the system. When thermostat 26 determines that the temperature of the winter-heated space 48 is below a predetermined minimum temperature, or for example when the temperature on the thermostat is increased, the thermostat queries a ceiling temperature sensor 70 that is located above the winter-heated space 48 and measures the air temperature at the sensor. In FIG. 1, ceiling temperature sensor 70 is shown near the apex of the vaulted ceiling. It will be appreciated that multiple sensors 70 may be used, and their locations may vary. Temperature data from sensor 70 is communicated to microprocessor 62 and the ceiling temperature data is compared to temperature data measured at thermostat 26, which also is communicated to microprocessor 62. Microprocessor 62 is preprogrammed with information and instructions for operation of heating and cooling system 10. If the temperature measured at sensor 70 is significant enough that heat may be recovered by operation of structure source loop 20, microprocessor 62 actuates valves 58 and 60 as described above to select the structure source loop and fluid flow through the structure source loop is initiated by microprocessor 62 activating pump 59. Thus, microprocessor 62 will initiate operation of structure source loop 20 is the difference in the temperature measured at thermostat 26 and temperature sensor 70 is greater than a predetermined minimum that is programmed into the microprocessor. Once the structure source loop is activated and pump 59 is turned on, heat exchange fluid flows through the conduits. As the exchange fluid in tubing 46 warms as it passes over the winter-heated space and flows back into geothermal heat pump 16, heat is extracted in the heat pump as warmed air (geothermal heat pump 16 is in this instance a medium-to-air exchanger). The geothermal heat pump 16 is operated in conjunction with furnace 14 to direct the warm air derived from the exchange fluid flowing through tubing 46 into the winter-heated space 48 through ducting 28 by operation of fan 29. Depending upon the difference between the temperature at ceiling temperature sensor 70 and thermostat 26, operation of the structure source loop 20 may be delayed while furnace 14 is operated by itself to provide supplemental heat to raise the temperature of the winter-heated space 48 until the temperature measured at sensor 70 meets a predetermined level where operation of the structure source loop 20 is determined by microprocessor 62 to be desired. The furnace may be operated with the furnace fan only, in which case heat drawn off the warm side of the structure source loop is used to heat structure 12. In other instances the supplemental heating system in furnace 14 may be operated simultaneously with geothermal heat pump 16 to heat structure 12. When the temperature at thermostat 26 reaches the predetermined or preset level microprocessor 62 controls and operates furnace 14, geothermal heat pump 16 and structure source loop 20 to maintain the desired temperature (as measured at thermostat 26). As the interior temperature of structure 12 rises, the warm air in the structure rises toward the ceiling. This heated air warms the fluid circulating through the tubing of structure source loop 20 so the heat is efficiently recovered by heat pump 16. This minimizes the amount of supplemental heat that is required from furnace 14 and thus minimizes energy consumption.

It will be appreciated that the structure source loop 20 will be used primarily in the winter months as a means of recovering heat from the warmed interior of a building. However, structure source loop 20 may be used for cooling as well. Consider for example a circumstance where the air temperature outside of structure 12 is relatively high, as in summer months, and the temperature at sensor 70 is lower than the temperature that is entered into thermostat 26. In such instances the structure source loop may be operated so that air that is at a temperature lower than that entered into the thermostat is circulated in the structure. Structure source loop 20 thus defines a method of recovering heat that is generated in a structure, and re-using that heat to warm the structure.

If heating and cooling system 10 includes a ground source loop 18 and a structure source loop 20, microprocessor 62 is preprogrammed to select either the ground source loop 18 or the structure source loop 20 depending upon which loop will provide the most efficient heat exchange. As shown in FIG. 1, a ground temperature sensor 72 is placed in the ground and communicates ground temperature data to microprocessor 62. Generally stated, if the air temperature at thermostat 26 indicates that either heating or cooling is necessary, microprocessor 62 queries the temperature sensors 70 and 72 and compares those temperatures with the temperature at the thermostat. Assuming the temperature difference between the thermostat and one of the sensors is sufficient that the heating and cooling system 10 is operable in an efficient manner—which is determined by preprogrammed instructions in microprocessor 62—the microprocessor selects the source loop that can deliver exchange fluid to the heat pump at a temperature that is closest to the temperature at the thermostat. Accordingly, the selected source loop, i.e., either ground source loop 18 or structure source loop 20, is the one that would take less energy to change the temperature inside the structure to the desired temperature. Thus, in this situation microprocessor 62 will always select the source loop at which the temperature is closes to the temperature desired at thermostat 26.

Operation of the ground source loop 18 is identical to operation of the structure source loop 20 described above. Thus, when thermostat 26 determines that the temperature of the winter-heated space is below a predetermined minimum temperature, or when a specific temperature is entered into the thermostat, the thermostat queries both ceiling temperature sensor 70 and ground temperature sensor 72. Temperature data from sensors 70 and 72 is communicated to microprocessor 62 and the temperature data are compared to temperature data measured at thermostat 26. Microprocessor compares temperature data from sensors 70 and 72 and determines whether heat may be recovered from one of the loops (i.e., either structure source loop 20 or ground source loop 18), and if so, which loop will provide the most efficient heat exchange. In this example, assuming that microprocessor 62 compares temperature data from sensors 70 and 72 and determines that more heat may be recovered from ground source loop 18, microprocessor 62 operates valves 58 and 60 to select the ground source loop and fluid flow through the ground source loop is initiated. Geothermal heat pump 16 is operated either alone or in conjunction with furnace 14 to direct warm air into the winter-heated space 48 through ducting 28. As with the structure source loop 20, depending upon the difference between the temperature at ground temperature sensor 72 and thermostat 26, operation of the ground source loop 18 may be delayed while furnace 14 is operated by itself to raise the temperature of the winter-heated space 48 until the temperature difference between the two points meets a predetermined level where it operation of the ground source loop 18 is determined to meet predetermined efficiency criteria programmed in the microprocessor. And as noted earlier, the furnace may be operated with the furnace fan only, in which case heat drawn off the warm side of the ground source loop is used to heat structure 12. In other instances the heating system in furnace 14 may be operated simultaneously with geothermal heat pump 16 to heat structure 12.

When the temperature at thermostat 26 reaches the predetermined level microprocessor 62 controls and operates furnace 14, geothermal heat pump 16 and a selected loop 18 or 20 to maintain the desired temperature (as measured at thermostat 26). Thus, in a structure 12 that includes both a structure source loop 20 and a ground source loop 18, the microprocessor continuously queries temperature sensors 70 and 72, compares temperature data to determine which loop would be most efficient, and operates the heating and cooling system 10 accordingly.

Typically, a ground source loop 18 is relied upon more in the summer months with a structure 10 that includes a structure source loop 20. An example illustrates the foregoing. Assume that the temperature in the interior of structure 12 is 65° F. and an occupant sets thermostat 26 to 72° F. Thermostat 26 communicates that data to microprocessor 62. In this example, assume further that the temperature measured at sensor 70 is 78° F., and that the temperature measured at sensor 72 is 55° F. Microprocessor 62 compares these data from sensors 70 and 72 and because the temperature at sensor 72 is below the temperature entered into thermostat 26, will not select ground source loop 18. On the other hand, the temperature at sensor 70 for structure source loop 20 is greater than the temperature entered into the thermostat. Accordingly, if the difference between the temperature at sensor 70 and the temperature entered into thermostat 26 is greater than a preset minimum difference programmed into microprocessor 62, the microprocessor will initiate selection and operation of the structure source loop as described above. The preset minimum temperature difference programmed into microprocessor 62 for initiation of one of the heating and cooling loops is determined by many factors, including the efficiency of the system, the local climate, etc. and may be varied as necessary in any particular installation. In a different example, if the difference between the temperature at the thermostat and the temperature at sensor 72 exceeds a predetermined minimum, and the temperature at sensor 72 is greater than the temperature at sensor 70, then the controller will select the ground source loop 18 and will initiate operation of that loop.

It will be appreciated that the heating and cooling system 10 operates in a like manner when cooling of the structure is desired.

It will further be appreciated that various equivalent heating and cooling systems may be made by modifying the foregoing described embodiments. For example, the tubing 46 of structure source loop 20 may be replaced by a membrane-like sheet having fluid channels formed therein, where the membrane is installed between the heated interior space 48 insulation 56. Those of ordinary skill in the art will understand that other similar modifications will result in an equivalent apparatus for recovering heat from the interior of the structure via heat exchange fluid flowing above the heated interior space.

Having here described illustrated embodiments of the invention, it is anticipated that other modifications may be made thereto within the scope of the invention by those of ordinary skill in the art. It will thus be appreciated and understood that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims. 

1. A heating and cooling system for a structure having a heated interior space and a roof, comprising: a furnace; a heat exchanger; a fan for inducing a flow of air from the heat exchanger to the interior space; a first conduit capable of conducting a flow of a heat exchange medium, said first conduit operatively connected to the heat exchanger for conducting the heat exchange medium through the heat exchanger, and said first conduit including a length of conduit located between the heated interior space and the roof; and insulation between the conduit and the roof.
 2. The heating and cooling system according to claim 1 including a thermostat in the heated interior space and a first temperature sensor located between the heated interior space and the roof, a pump for inducing a flow of the heat exchange medium through the first conduit and a controller in communication with the thermostat and the first temperature sensor, said controller configured for operation of the furnace, the fan, the heat exchanger and the pump.
 3. The heating and cooling system according to claim 2 wherein said controller further includes a microprocessor configured for comparing temperature data from the thermostat and the first temperature sensor, and for operating the furnace, heat exchanger and pump if the difference between the temperature at the thermostat and the temperature at the first temperature sensor exceeds a predetermined minimum.
 4. The heating and cooling system according to claim 2 including a second conduit for conducting a flow of a heat exchange medium, said second conduit operatively connected to the heat exchanger and a pump for conducting the heat exchange medium through the heat exchanger, and said second conduit including a length of conduit buried in the ground and a second temperature sensor buried in the ground and in communication with the controller.
 5. The heating and cooling system according to claim 4 wherein said controller includes a flow controller and the first conduit and second conduit are operatively connected to the flow controller, and said flow controller is in operative communication with said microprocessor, whereby said microprocessor is capable of selecting either said first conduit or said second conduit.
 6. The heating and cooling system according to claim 5 wherein said controller is configured for comparing temperature data from the thermostat and the first and second temperature sensors, and for selecting either the first conduit or second conduit based on predetermined criteria and operating the furnace, the fan, the heat exchanger and pump in response to the selection.
 7. The heating and cooling system according to claim 6 wherein said controller selects the first conduit if the difference between the temperature at the thermostat and the temperature at the first temperature sensor exceeds a predetermined minimum.
 8. The heating and cooling system according to claim 6 wherein said controller selects the second conduit if the difference between the temperature at the thermostat and the temperature at the second temperature sensor exceeds a predetermined minimum, and the temperature at the second temperature sensor is greater than the temperature at the first temperature sensor.
 9. A method of recovering heat in a structure having a heated interior space, an insulated roof above the heated interior space, and a furnace, comprising the steps of: (a) installing a first conduit above the heated interior space and below the insulated roof; (b) operatively connecting said first conduit to a heat exchanger and operatively connecting said heat exchanger to said furnace; (c) inducing a flow of a heat exchange medium through said first conduit so that the temperature of said heat exchange medium is raised as it flows through said conduit, and circulating said heat exchange medium through said heat exchanger; (d) extracting heat from said heat exchange medium in said heat exchanger to warm air; and (e) inducing a flow of said warmed air into said heated interior space.
 10. The method according to claim 9 including the steps of: (a) measuring the temperature in the heated interior space; (b) measuring the temperature above the heated interior space and below the roof; (c) comparing the temperatures measured in steps (a) and (b) and in response thereto, determining if a flow of the heat exchange medium should be induced through the first conduit.
 11. The method according to claim 9 wherein if the difference between the temperature measured at steps (a) and (b) exceeds a predetermined minimum, inducing a flow of the heat exchange medium to increase the temperature of the heat exchange medium, extracting heat from the heat exchange medium in the heat exchanger to warm air, and operating said furnace to induce a flow of said warmed air into said heated interior space.
 12. The method according to claim 11 wherein if the difference between the temperature measured at steps (a) and (b) is below the predetermined minimum, the furnace is operated to heat the heated interior space.
 13. The method according to claim 9 including the steps of: (a) installing a second conduit in the ground; (b) operatively connecting said second conduit to the heat exchanger; (c) placing the first and second conduits, the furnace and the heat exchanger under the control of a controller; (d) causing the controller to select either the first or the second conduit in and inducing a flow of a heat exchange medium through the selected first or second conduit so that the temperature of said heat exchange medium in said selected conduit is raised as it flows through said selected conduit, and circulating said heat exchange medium through said heat exchanger; (e) extracting heat from said heat exchange medium in said heat exchanger to warm air; and (f) inducing a flow of said warmed air into said heated interior space.
 14. The method according to claim 13 including the steps of: (a) measuring the temperature in the heated interior space; (b) measuring the temperature above the heated interior space and below the roof; (c) measuring the temperature of the ground, and (d) comparing the temperatures measured in steps (a), (b) and (c) and in response thereto, determining if a flow of the heat exchange medium should be induced through the first conduit or the second conduit.
 15. A heating and cooling system for a structure having a heated interior space and an insulated roof over the heated interior space, comprising: furnace means for heating the interior space; fan means for inducing a flow or air into said interior space; heat exchanger means for extracting heat from a heat exchange medium conducted through the heat exchanger, the heat exchanger means operatively connected to the fan means; first conduit means for conducting said heat exchange medium through the heat exchanger means and over the heated interior space, said first conduit means at least partially located above the heated interior space and below the insulated roof; controller means for initiation of a flow of the heat exchange medium through the first conduit means, and for controlling operation of the furnace means, fan means and heat exchanger means.
 16. The heating and cooling system according to claim 15 further comprising a thermostat in the heated interior space and air temperature sensing means located between said heated interior space and the insulated roof for measuring the air temperature at said temperature sensing means, said thermostat and temperature sensing means configured for communicating with said controller means.
 17. The heating and cooling system according to claim 15 wherein said first conduit means further comprises a closed loop conduit extending from said heat exchanger means over said heated interior space.
 18. The heating and cooling system according to claim 17 wherein said first conduit means includes pump means for inducing a flow of heat exchange medium through said closed loop conduit.
 19. The heating and cooling system according to claim 16 further including second conduit means for conducting heat exchange medium through the heat exchanger means, said second conduit means at least partially located in the ground.
 20. The heating and cooling system according to claim 19 including ground temperature sensing means for measuring the temperature of the ground and communicating with said controller means, and wherein said controller means is capable of selecting either the first conduit means of the second conduit means based on temperature data received from the thermostat, the air temperature sensing means and the ground temperature sensing means. 